Sybrina Fulton and Tracy Martin, the parents of Trayvon Martin, the unarmed Florida teen shot dead by a neighborhood watch volunteer, tell TODAY's Matt Lauer they want justice for their son and want the shooter, George Zimmerman, arrested.

By msnbc.com staff and news services

Updated at 7:48 a.m. ET: Florida’s 2005 “Stand Your Ground” law, which says a citizen doesn’t have to retreat before using deadly force against an attacker, could throw a legal wrinkle into the case of a neighborhood watch captain who shot to death an unarmed black teenager.

Police in the central Florida town of Sanford have said that 28-year-old George Zimmerman says he shot 17-year-old Trayvon Martin in self-defense during a confrontation in a gated community. Police have described Zimmerman as white; his family says he is Hispanic and not racist.

Police did not arrest Zimmerman after the shooting, but State Attorney Norm Wolfinger announced Tuesday the case will go before a Seminole County grand jury.

Richard Hornsby, an Orlando-based criminal defense attorney, says he thinks the grand jury is likely to indict Zimmerman for manslaughter, a second-degree felony punishable by up to 15 years in prison. Less likely is a more serious charge of second-degree murder, a crime that implies intent and that is punishable by up to life in prison, he said.

Trayvon Martin's final phone call -- made to his girlfriend -- is shedding new light on the moments leading up to his deadly confrontation with a neighborhood watch volunteer. NBC's Lilia Luciano reports.

“This case isn’t even a close call to me. This is a case of a guy trying to be a vigilante,” Hornsby said. “It wasn’t like he was trying to avoid trouble. He brought a firearm to a fistfight.”

“My gut feeling he will ultimately be charged with some type of manslaughter charge,” agreed Philip Sweeting, retired deputy police chief for the Boca Raton Police Department and a law enforcement consultant who has testified in court cases as an expert in police shootings and use of force.

Watch the entire news conference.

“My gut reaction was this was an accidental discharge,” Sweeting added. “If you put yourself in the shooter’s position and you’re wrestling with this kid and a gun goes off, what are you going to tell the cops?”

If indicted, Zimmerman can raise the Stand Your Ground defense under the 2005 law signed by Gov. Jeb Bush. That legislation, derisively called the “Shoot First” law by its critics, gives Floridians the right to use deadly force to defend themselves in public places without first trying to escape. The National Rifle Association lobbied hard for the bill, saying it would allow citizens to better protect themselves from violent crime.

A person who is not engaged in an unlawful activity and who is attacked in any other place where he or she has a right to be has no duty to retreat and has the right to stand his or her ground and meet force with force, including deadly force if he or she reasonably believes it is necessary to do so to prevent death or great bodily harm to himself or herself or another or to prevent the commission of a forcible felony."

Hornsby says the 2005 bill allows Zimmerman’s lawyers to argue to a judge – before any trial -- that the case should be dismissed on grounds he was permitted to defend himself. If the case isn’t dismissed, they could argue self-defense at trial.

Daniel Vice, senior attorney with the gun-control group Brady Center to Prevent Gun Violence, contends “Stand Your Ground,” combined with Florida laws allowing people to carry guns in public, have made it difficult to pursue criminal charges against people who shoot others and then say it was self-defense.

“All you have to say is that you reasonably believed you were threatened, and the only person who can dispute that is the person you have just killed,” Vice says.

"It's very hard to bring these types of cases because the 'Shoot First' law combined with public carrying of loaded guns protects people who engage someone and shoot to kill."

According to a 2010 review by the St. Petersburg Times, reports of justifiable homicide tripled after the law went into effect. It has been invoked in at least 93 cases with 65 deaths, used to excuse violence in deadly neighbor arguments, bar fights, road rage and even a gang shootout, the newspaper reported.

Gun-rights advocates say the facts to date are scarce and “Stand Your Ground” may or may not apply in this case.

According to transcripts of the 911 calls, a police dispatcher tells Zimmerman he doesn’t need to follow the teen, but Zimmerman apparently does anyway. So is he or the teen the one who feels threatened?

The Department of Justice has launched an investigation into the death of the teen shot in the picturesque city of Sanford, Fla. NBC's Ron Allen reports.

“The question again is whether he (Zimmerman) acted reasonably or not. At this point it doesn’t look good for him, but I don’t know what the heck happened and quite frankly no one else does either,” says Jon H. Gutmacher, an Orlando attorney,NRA-certified instructor and author of "Florida Firearms: Law, Use & Ownership."

“When you’re talking about law and whether things were legal and illegal, you can’t guess. You’re supposed to react to facts. The facts have been kept from the public and the press.”

Added Dave Workman, director of communications for the Citizens Committee for the Right to Keep and Bear Arms: “There’s a misunderstanding about what Stand Your Ground laws really do. No Stand Your Ground law translates to a broad permission for the use of lethal force when it’s not warranted.”

He added: “A lot of people have left the starting gate before they really know what has happened. A rush to judgment is never a good thing.”

The Associated Press, Reuters and msnbc.com's James Eng contributed to this story.